Laundry dryer control mechanism



Feb. 25, 1964 s. v. HORECKY LAUNDRY DRYER CONTROL MECHANISM 2Sheets-Sheet 1 Filed June 27, 1961 FIG. 3

FIG. 4

INVENTOR. STANLEY V. HORECKY BY MW ATTORNEY Feb. 25, 1964 s. v. HORECKY3,122,426

LAUNDRY DRYER CONTROL MECHANISM Filed June 27, 1961 2 Sheets-Sheet 2 0 uN TLZ lb-III I FIG. 6

INVENTOR. STANLEY V. HORECKY ATTORNEY United States Patent O 3,122,426LAUNDRY DRYER CONTROL MECHANISM Stanley V. Horecky, Oak Park, Ill.,assignor to General ElectricCompany, a ccrporation of New York FiledJune 27, 1961, Ser. No. 119,973 13 Claims. (Cl. 34-45) This inventionrelates to laundry dryers and more particularly to mechanisms forcontrolling the operative cycle of these dryers.

The art contains numerous examples of controls to provide a fullyautomatic dryer; that is, a dryer having a simplified control whichcould be set at the start of the operation and would continue the dryinguntil a sensing mechanism determined that the laundry was dry. In mostforms of these controls,- the dryness of the laundry was estimated bysensing various physical conditions within the drum. Some sensed theexhaust air temperature and reacted to changes beyond a predeterminedamount. Others sensed the moisture content of the exhaust air and endedthe cycle when this moisture content decreased. However, it isdifllcult, in the practical sense, to correlate air temperature orhumidity to actual clothes dryness, and most contemporary systems ofclothes dryer control, in which drying operation is terminated when sucha physical condition has reached the control point, are at best, only ofan approximating nature. It would appear to be more reasonable to sensethe actual moisture condition of the laundry within the drum. In US.Patent 2,820,304, issued on January 21, 1958, to the present inventor,there is shown one form of mechanism for approximating the actualmoisture content of the laundry being dried. The present inventionprovides improved means for actually sensing the moisture content in thelaundry, and to an improved control circuit for evaluating the apparentmoisture content and terminating the dryer operation as required.

It is therefore an object of the invention to provide an improvedlaundry dryer control which directly senses the dryness condition of theclothes being dried.

It is a further object of the invention to provide a mechanism with aplurality of moisture-sensing electrodes dispersed about the peripheryof the drum to maintain the dryer in operation until the clothes haveattained a desired condition of dryness.

Other objects, features and advantages of the invention will becomeapparent with reference to the following specification viewed with theaccompanying drawings in which: g

FIG. 1 is a perspective View of a dryer utilizing my invention, with thecabinet shown in phantom View and portions of the drum, etc., brokenaway to reveal otherwise concealed structure;

FIG. 2 is a schematic side sectional view of the dryer of FIG. 1 toillustrate air movement therein;

FIG. 3 is a side sectional View of the drum interior;

FIG. 4 is a front sectional view of the drum;

FIG. 5 is a schematic diagram of a control circuit for the dryer;

FIG. 6 is a partial section of the drum sidewall;

FIG. 7 is a partial view from the rear of the slip ring arrangement; and

FIG. 8 is a front view in detail of the control knob of FIG. 1.

In FIG. 1 is shown a dryer 10 having conventional means for circulatingair through the clothes as they tumble within the drum. It will beunderstood, however, thatthe invention is not restricted to anyparticular air circulation or drying means, for it is the dryness of theclothes load itself, and not the physical condition of the circulatingair, which is determined by the present invention. A conventionalcabinet 12 has front, top, side 3,122,426 Patented Feb. 25, 1964 andrear walls. An access opening 14 is provided in the front wall, theopening being covered by a side hinged door 16 shown in the closedposition in FIG. 2. At the top rear of the cabinet is mounted anenclosed control area 18 in which the necessary electrical controls arefitted. Extending forwardly from this area are the manuallymanipulatable control knob 19 and a multiple selection switch 20. Thisswitch has a plurality of pushbuttons whereby the operator may selectlow heat upon pushing button 20.1, high" heat by pushing button 20.2,and no heat when it is desired merely to fluif the clothes by tumblingthem in the absence of heat. Switch 20 may advantageously be of the typedisclosed in'Andrews US. Patent 2,431,904, granted December 2, 1947. Insuch a switch, pressing one button will operate any previously-pressedbutton to return to an unoperated position. The switch 99 (FIG. 5)operated by button 20.3is opened when the button 20.3 is pressed, andreturns to closed condition when the button is projected, whereuponpressing either button 20.1 or 20.2 will complete a heater circuit.Operating button 20.1 will open switch 98; operating button 20.2 willclose switch 98.

Within the dryer cabinet there is included a drum 22 rotatable on ahorizontal axis. Consistent with the illustrated air circulation system,the sidewall of the drum is imperforate. Spaced about the sidewall 23are the inwardly directed, substantially triangular, lifting vanes 24,each of which extends for the entire axial length of the sidewall. Therear wall 26 of the drum is perforated to allow passage of air into thedrum and at the front of the drum there is a circular opening 28 inregistry with the cabinet opening to afford access to the drum interior.Consistent with contemporary practice, the drum will have a vitreousenamel coating, and, therefore, the inner surface of the drum will beelectrically non-conductive.

To dry laundry being tumbled within the drum, a stream of heated air iscirculated through the drum axially. This air receives moisture from thelaundry being dried. The air circulation system includes in the cabinetrear wall a plurality of air inlet openings 30 which may be louvered asshown. A louvered circular heater casing or shroud 32 envelops therearend of the drum and is mounted stationarily to the cabinetstructure. Within the shroud are afiixed a plurality of concentricheater elements 34, 34a, illustratively comprising helically woundresistance wire in heat exchange relation with air passing thereover.The electric heaters merely typify a heating system; gas-burningheaters, under control of a conventional electrical control device suchas a relay or solenoid, may be used without departure from theinvention, as Will be later apparent.

Air circulation is enforced by a suction producing network which inducesair flow into the drum. Air leaving the front opening of the drum entersthe exhaust ducting system at the entrance 36 at the bottom of theinter-space between the drum and the cabinet. This entrance may leadthrough a conventional lint filter (not shown) to a downwardly directedduct 38 and into the blower chamber 49 from which the air enters a ductwhich conveys the exhaust air out the rear of the cabinet.

The blower chamber 40 includes an air impelling rotor 41 of conventionaldesign and driven by the drivemotor 42 which is common to the fan andthe drum drive mechanism, which may comprise any conventional powertransmission system, such as a belt and sheave system (not shown). Atthe front the drum may be cradled on suitable resilient rollers 44adjacent the drum access throat 46. Further the drum is maintained inits fixed rotating pattern by means of an axial stub shaft 48 securedconcentrically to the drum rear wall and maintained rotatably insuitable stationary bearings mounted on the cabinet rear wall.

The structure described to this point is quite conventional and isillustrated in many patents of the prior art. The present inventionresides in the control mechanism for the dryer which will now bedescribed. As shown in FIG. 3, circularly disposed about the interior ofthe drum sidewall are four pairs of parallel electrodes 51. Theseelectrodes which may be considered as bare wires are insulated at allpoints from contact with the adjacent sidewall by imbedding the wires insuitable strips 52 of heat and moisture resistant, and electricallyinsulating materials such as the presently known silicones.

Each of these wires describes a single circular loop within the circularsidewall. lllustratively, there are eight parallel loops about thesidewall arranged in four pairs, respectively identified as al, a2; b1,b2; 01, c2; and (ill, One of the ends of each loop is dead ended; theother end is multipled to the corresponding end of the loop once removedfrom the loop in question. In short, every other loop has one endconnected in multiple as shown in FIG. 6. One end of loops al, bl, cland (ii is connected in multiple and is connected to slip ring 6t Theotier multiple from loops (12, b2, c2 and d2 is connected to outer slipring as. These slip rings may be of any conventional design which allowsgood electrical contact from an annular rotating conductor to a conductor connected to a brush riding on the slip ring. The respectivebrushes, 64, 66 may be mounted from the shroud 32 by suitable insulatedsupports. The leads from brushes 64 and 66 are connected into a moisturecontent sensing circuit (FIG. The circuit is connected to a conventionalEdison three-wire source to provide 236 volts across leads L1 and L2 and118 volts across the intermediate lead N and either one of the outerleads L1 or L2.

Within the circuit of FIG. 5, there is shown a conventional timer motor7% which may be set manually by manipulation of knob 9 for either anormal timed operation or automatic dry (see FIG. 7). The timer controlsa plurality of switches which are operated by cams C1C4 positioned to berotated by the timer motor and having associated therewith springs whichare actuated or released at specific times by the cam action. Suchtimers are well known and understood by those skilled in the art.Specifically, there is a first set or" switch contacts '72 which controlthe operation of the timer motor and are closed when the operator wishesto operate the dryer on a purely time basis. As is well known, the knob1% is rotated manually to the desired registry of the minute markings15, 30, 45, etc., with the index 13, whereupon the switch 72 will closeand remain closed until the selected time has elapsed, whereupon thedryer operation will terminate. A second set of contacts "/4 serve toconnect the automatic sensing network onto the power source whenautomatic drying is selected. A third set of cam-controlled contacts 76serve to complete the operating path to the drive motor and must beclosed for operaing the drive motor during the timed dry period. A finalset of contacts 78 complete a path to the heating units 34 and 34aofheater shroud 32. In the circuit to lead Ll, there can be seen amotor-operated switch 82 which is closed whenever the drive-motor 42 isrunning at its operating speed and opens the circuit to the heaters onslow down of the motor. Further in series with switch 82 is theoperating thermostat 84. Thermostat d4 serves to cycle the heater orheaters during the operative cycle to maintain the air temperature ofthe drum at a fairly constant level. In the line connection from L2there can be seen a conventional door switch d6 which opens the linecircuit to the drive motor, the timer motor and the heaters on openingof the door. A second set of contacts 86.1 of door switch 86 isconnected in the Lil side of the heaters so that both sides of theheater circuit are opened on opening of the door. A high temperature orshut-off thermostat 88 is placed in series with the door switch to shutdown the machine on occurrence of a high temperature in the dryer.

The drive motor 42., having the usual start winding 90, run winding 92and centrifugal switches 32 and 94, is connected between the neutralconductor N and contacts of momentary or safety start switch 95 toobvious circuit components leading to conductor L2. Momentary switch 95also includes a second set of contacts 97 which are effective in theautomatic drying cycle, as will be explained in detail. This switch mustbe depressed to start the cycle and releases on release of fingerpressure by the operator. If the dryer is shut ofi in mid-cycle, switch9 5 must be depressed for reset. The regular operating circuit alsoincludes a low-temperature setting switch 98 which is opened when thetemperature at which the machine is to be operated is set at lowtemperature. With switch 98 open, the energizing path to heater coil34:: is opened and only heater 34 remains in the circuit. To allow theclothes to be fiuif-dried (tumbling in the drum with no heat) afiutl-switch 99 may be provided. When the operator presses control panelbutton 241.3, this switch 99 opens the circuit to the heaters and thisswitch will remain operated until released by pressing either of thebuttons 2611 or 20.2, as earlier explained.

The automatic drying circuit includes among its components a pair ofrelays. A first relay 100 is of the marginal electromagnetic type and isquick to pull in, and slow to release. This relay controls its normallyopen contacts 162, 31M and 106 to close these contacts on operation inthe generally known manner. For example, relay 106* may require onlyabout a millisecond of energization for it to operate. The circuit torelay coil 101 includes a capacitor 168 which tends to speed theoperation and to slow the release of the relay. Capacitor lili maintainsthe relay to hold its contacts closed for about ten seconds aftercessation of the relay-energizing pulse. The second relay lid is oi thetype which closes its contacts 1.12 and 114- after about five seconds ofenergization of its coil lid and remains operated with its contactsclosed for about two minutes after the power has been interrupted to therelay coil. Relay 116' may be a conventional resistance coil-heatedbi-metal type which operates its contacts on heating of its coil andreleases these contact after its coil circuit has been interrupted fortwo minutes. The circuit further includes a rectifier I i-6 connectedserially through capacitor 168 and current limiting resistor 11% to theelectrodes via brushes 64, 66 and slip rings ea, 62. This circuit servesto supply half wave rectified direct current for energizing the relays,etc. Further there is provided a switch 124- which is operated to eitherof two circuit closing positions as the knob d9 is turned from its ofidesignation to either the dry or the damp dry indexes of the knob. Aglow-discharge device such as the neon bulb 126i is connected to aresistor 1'22 and then directly to contact 128 of switch 124, or by Wayof the resistor 126, to contact 129' of said switch. It is obvious fromHG. 5, that either resistor 122 or both resistors 122 and 126 areconnected between relay ltltl and ground, according to whether the relaycoil is in circuit with contact 3123 or contact 129 of switch 124-. Aspresently appears, this will be determinative of the end clothescondition which will shut ed the dryer. The switch 124 would be closedto contact 128 for automatic drying to the bone dry clothes condition,and to the 129 contact if a damp-dry condition is required.

The following table states the operating condition of the respectivecam-operated switches in the time-dry and automatic dry control knobsettings:

Cam Switch 'lime Dry Automatic Dry C1 72 Closcd Open. 76 Closed Open. 78Closed..- Open. 04 74 Open Closed.

Timed drying of the system is quite conventional and operates asfollows: Knob 19 is rotated to the position indicating timed drying andis set at the time required for drying the'load in question. The manualrotation of the knob rotates cams C1, C2 and C3 to close theirassociated cam-operated contacts 72, 76 and 78. At contacts 72, thetimer motor 78 is closed to the ll8-volt source over a path which can betraced from lead L2, through the closed door switch 86, high limitthermostat 88, closed contacts 72, timer motor 70 to lead N and ground.The timer then starts its operation of returning the output carn shaft73 to the Off position at a fixed rate in a generally known manner.

Nothing further will occur until the momentary start switch 95 isdepressed closing'its contacts 96 and 97. Contacts 97 have no eifeotduring this timed operation and their closure may be ignored. Atcontacts 96, the drive motor 42 windings are energized over a path whichmay be traced from ground at lead N through the parallel windings (startwinding 90 and run winding 92), the normally closed upper contacts ofcentrifugal switch 94, contacts 96, closed timer contacts 76, to thehigh limit thermostat 88, and closed door switch 86 to lead L2. Themotor 42 accelerates rapidiy and centrifugal switch 82 closes :andswitch 94 closes on its lower contacts. This opens the start windingcircuit, and the motor continues on the run winding 92 through conductor130 and timer contacts 76. As contacts 82 close, heater 34 alone (if lowheat has been selected) or both heaters 34 and 34a it high heat switch98 has been closed, are energized. The heater. circuit may be followedfrom lead L1, through motor switch contacts 82, thermostat 84, doorswitch contacts 86.1, heater 34, normally closed contacts 99, camcontacts 78, thermostat 88, and closed contacts 86 to lead L2. If highheat is required, high heat switch 98 is closed by manual operation ofswitch button 201 on control panel 18 to place heater 34a in parallelwith heater 34. With either temperature selection, thermostat 84 cyclesto maintain the temperature in the dryer relatively constant byshuttingoif the heaters on reaching a predetermined high temperature andenergizing the heaters on the air in the dryer reaching a preset lowtemperature, as is well known in the art. The drying cycle continues inthis manner until the selected timed period approaches completion, atwhich time cam contacts 78 open deenergizing the heaters and allowingthe drum to rotate for a cool down period which may be of five minutesduration or less. At the conclusion of this period, contacts 72 and 76open their respective circuits and the dryer is shut off. i I d Forautomatic drying there is a choice of damp dry or bone dry; theoperation in either instance is virtually identical. In operating themachine for bone-dry clothes, the control knob 19 is rotated until 1 thesection marked Dry-A-utomatic is positioned under the positioning arrow13 (FIG. 8). Movement of the knob to this position closes contacts 74 ofcam C4 and operates the automatic dry switch 124 to close against itscontact 128. This closure completes a path to neon lamp 120 over acircuit from lead L2 through door switch contacts .86, high temperaturethermostat 88, contacts 74, rectifier 116, winding of relay 100, switchcontacts 124, 128, resistor 122, and to ground. Lamp 120 then fires toindicate the circuit is prepared for automatic drying. This closure alsocompletes a resistive circuit to relay 100, but the combined eifect ofthe half wave current passing through rectifier 116, the capacitiveeffect of capacitor 108, the resistance of resistor 122, and themarginal adjustment of the relay combine to keep the relay fromoperating at this time. Cam C1 is so arranged that when the knob 19 isrotated to either of its automatic settings, contacts 72 are not closed,hence no timing occurs with p the knob 19 in this position. Contacts 74remain closed I for the duration of the automatic drying period.

Shortly after knob 19 is positioned to automatic dry, and neon bulb 120has fired, momentary start switch 95 v 6 is depressed closing itscontacts 96 and 97. Contacts 96 serve no useful function for automaticdry but contacts 97 on closure initiate the sequence of operations toprovide automatic dryness sensing. Momentary closure of switch connectsthe grounded N lead through contacts 97, conductor 103 contacts 128 ofswitch 124 through the winding 101 of relay and conductor to rectifier116, contacts 74, thermostat contacts 88 and door switch contacts 86 tolead L2. This closure shunts out resistor 122 and neon lamp so thatthese components are no longer effective. Lamp 120 then ceases firing to(indicate the automatic cycle has begun. Relay 100,

being of the quick-to-operate type, operates on receipt of the groundpulse from contacts 97 and will remain operated for a period of tenseconds following cessation of its operating pulse. On operation, relay100 closes its contacts 102, 104 and 106. Contacts 102 complete acircuit from lead L2 for the motor run circuit, and the motor beginsoperation at once. Contacts 104 on closure complete a circuit toenergize time delay relay 110. This operating path for relay 110 may betraced from ground at lead N through relay winding 111, closed contacts104, thermostat 88, door switch contacts 86 to lead L2. Aiter a delay ofabout five seconds (relay 100 once having operated thus maintaining itscontacts 104 closed for ten seconds) relay lltloper-ates closing itscontacts 112 and 114. At contacts 112, a parallel circuit is closed foroperation of the drive motor 42, said circuit maintaining motoroperation following the opening of relay contacts 102, as presentlyexplained. This circuit may be followed from lead N through motor startwinding 90 and motor-run winding 92 in parallel, conductor 115, closedcontacts 112 and 74 to thermostat contacts 88, door switch contacts 86and lead L2. Contacts 114 on closure act to ground the wetness sensorconductor, which as mentioned previously includes the electrodes a1, a2,b1, b2, etc.

It should be noted at this point that there must be wet laundry in thedrum for the operation of the circuit to continue for more than twominutes. With Wet laundry in the drum, a circuit is closed from groundthrough closed contacts 114, brush 66, slip ring 62 to electrodes a2-d2.With wet laundry anywhere in the drum distributed in virtually anyrandom fashion there will be a closed circuit from electrode al-dlmultiple to electrode a2d2 multiple. This closure will serve to connectthe previously mentioned ground at contacts 114 through slip ring 60 andbrush 64, contacts 128, relay 100,-rectifier 116 and closed contacts-74to the L2 side of'the line. Release of the relay 100 is further slowedby the R-C action of capacitor 108 and resistor 118 which aids inmaintaining relay operated by the resistance capacitive shunt across therelay. This capacitor cyclically charges and then discharges across therelay 100 aiding the normal operating path in maintaining the relayoperated. Relay 100 inturn maintains relay 110 operated so that the tworelays lock eachother operated through the sensor electrodes and the wetlaundry in the drum.

The motor accelerates and closes contacts 82 and the lower contacts ofswitch 94. Switch 94 therefore closes to lead 130, deenergizing thestart winding. Run winding 92 is energized from lead N through closedcontacts 102, 112 and 74 to thermostat contacts 88, door switch contacts86 to lead L2. On closure of motorspeed contact 82, the heater 34 isenergized over a path from lead L1, through contacts 82, thermostatcontacts 84, door switch contacts 86.1, heater coil 34, contacts 99,106, 104, thermo-, stat 88, and door switch 86 to lead L2. As with timeddrying, thermostat 84 cycles the heater to maintain a relativelyconstant air temperature in the drum throughout the drying cycle.

During the drying cycle, the drum tumbles at a nominal tumbling speed of50 rpm. or approximately one and onedifth seconds per revolution. Thusthe drum will complete about eight revolutions during a ten-secondperlod. During these eight revolutions, the electrode multiples must beshorted or the circuit must be closed with a low internal resistance atleast one time in order to provide relay till? with the necessaryoperating ground. During the early part of the drying operation, therelay lttl will receive many more than the amount of pulses necessary tokeep the relay and consequently dryer operative. As the dryingprogresses, the relay ldtl will continue to receive successi ely lessand weaker ground pulses until the laundry is quite Well dried. At thattime, during eight consecutive revolutions and the random tumbling ofthe laundry during those revolutions, the resistance across theelectrode multiples increases considerably and either Weak or noshorting pulses will reach the relay ltlll. Finally, the relay willrelease. Contacts 192, 1th; and 106 open. Contacts 164 on opening openthe circuit to time delay relay llilil. Opening of contacts 164 alsoserves to open the circuit to heater 34- which is thereby deenergized.

Relay llltl remains operated for about two minutes after the opening ofits energizing circuit. Thus, contact 132 remains closed for a period ofabout two minutes allowing continued operation of the rotor to provide acool down tumble of the drum for the two-minute period. At theconclusion of the cool down period, relay ill) will restore openingcontacts 112 and lid which opens the motor operating circuit and thedryer will come to a halt at the end of that period. Lamp 121 then firesover the previously described firing path and thereby signifies that theclothes are dry and the operative cycle has ended.

As mentioned previously, the ground path through neon lamp 120 andresistor 122 contains too much resistance to allow relay ltltl to becomeenergized or to hold relay lilh operated. Thus, as a practical matter,relay tilt) is maintained operated by the combination of the low amountof current passed by resistor 122 and that of the other parallel branchcircuit through the electrode multiple and the Wet clothes. Carryingthis viewpoint further, it can be seen that by increasing the resistanceof the branch parallel to that of the electrode multiple, the resistanceof the clothes determines to a greater extent the drop-out time of relayHill. This, in short, is the use accomplished by contact 129 of switch124. When damp dry clothes are desired, rotation of dial 1? to damp dryoperates switch 124 to engage contact 12%, placing resistor 126 inseries with resistor 122. The added resistance requires a lowerresistance and consequent higher current through the electrode multipleto maintain relay 1% operated. With this switch closed to its damp dryposition, relay Hill will retsore at a time when the resistance of theclothes is greater than at the time when the switch is in its dryposition.

A further advantage of the control circuit is apparent in the drying ofmaterials such as heavy terry-cloth robes or shag rugs. These materialscan exhibit a false appearance of dryness, in that the surface may bequite dry, while the heavy body will contain substantial moisture. Ifsuch articles were removed on the initial indication of dryness,migration of moisture through the loops of fabric by capillaryattraction will again make the articles sensibly damp to the touch. Inthe present invention, however, the two-minute tumble following therestoration of relay 1% affords opportunity for such movement ofmoisture again to dampen the outermost fibers, whereupon the sensorelectrodes will again have a low-resistance bridge. This restores propercircuit conditions for the reactivation of relay lltlil and resumptionof dryer operation until the dryness of the terry cloth or like fabricsinterrupts operation as previously described. It will be understood, ofcourse, that the two-minute time delay of the relay 110 is by way ofexample only, and that longer time delay can be built into the relay ifdesirable.

Further utilizing the circuit of FIG. 5, it can be seen that if themachine has shut ofi indicating clothes dry to the sensed level, and themachine operator does not consider this condition dry enough, reset ofthe machine will initiate a further two-minute tumble in the machine. Inthis instance, the resistance of the clothes is not sufficient to keeprelay 1% operated. The machine has restored. The dryness knob is stillon automatic dry. The operator depresses start switch 95, reenergizingthe motor, as previously described. A path is also closed from ground atlead N, through contacts 97, switch 124, relay ltlll, rectifier 116 andcontacts 74 to the lead to L2. Relay 1% operates, closes its contacts194, closes the circuit to relay llll. Meanwhile motor 42 and heater 34are reenergized. Relay lllil then falls back opening the heater path.Motor 42 continues to rotate for a period governed by the relay 110.This relay remains operated for two minutes as will motor 42, followingwhich both will again restore.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein, and it is intended to coverin the appended claims all such modifications as fall within the scopeof the invention.

What is claimed is:

1. In a laundry dryer including a drum mounted for rotation to tumblearticles of clothing therein, an electric heater to facilitateevaporation of moisture from said clothes, and an electric motoroperative to rotate said drum: the combination comprising a source ofelectric power, a first relay having a winding responsive to apredetermined value of electrical energy to operate said relay, electriccircuit means for first temporarily energizing said relay to operate thesame, switching means effective upon operation of said relay to energizesaid motor and said heater, a second relay having a winding, switchingmeans effective upon operation of said first relay to energize thewinding of said second relay to operate the same, switching meansoperated by said sec ond relay to provide a parallel energizing circuitfor said electric motor, other switching means operated by said secondrelay to prepare a circuit for maintaining energization of said firstrelay, means in said last named circuit responsive to contact by dampclothes within said drum for completing said circuit at an energy levelmaintaining operation of said first relay and responsive to a less dampcondition of said clothes to reduce said energy level below theoperational threshold of said first relay to thereby effect the openingof the switching means associated therewith; each of said relays beingof the slowto-release type, with the second relay delaying its releasefor a predetermined period after the release of the first, whereby tocontinue operation of said motor for said predetermined period.

2. The combination according to claim 1, further including timer meansfor terminating operation of said motor and said heater after apredetermined period of operation, and means whereby initiation of saidtimed operation will disable said first and second relays to prevent thesame from interfering with said timed operation.

3. The combination according to claim 2, in which the circuit fortemporarily energizing said first relay includes means for disablingsaid time-operation means and manually operable pushbutton switch meansof the momentary contact type.

4. In a laundry dryer including a drum mounted for rotation to tumblearticles of clothing therein, an electric heater to facilitateevaporation of moisture from said clothes, and an electric motoroperative to rotate said drum: the combination comprising a source ofelectric power, a first electrically energized relay responsive to apredetermined value of electric energy to operate said relay, electriccircuit means including a manually operable momentary contact switch fortemporarily energizing said relay to operate the same, switching meanselfective only upon operation of said relay to energize said motor 'andsaid heater, a second electrically energized relay, said first relayincluding switching means efiective upon initial operation thereof toenergize said second relay to energize the same, said second relayincluding first switching means effective upon operation thereof to provide a parallel energizing circuit for said electric motor and secondswitching means to prepare a circuit for maintaining energization ofsaid first relay, means responsive only to contact by articles havingnot less than a desired minimum electrical conductivity to complete saidenergizing circuit at an energy level maintaining operation of saidfirst relay and responsive to a condition of less conductivity of saidcontacting articles to reduce the energy level of said circuit below theoperational threshold of said first relay and thereby effect the openingof the switching means associated therewith; the second of said relaysdelaying its release for a predetermined period after the release of thefirst, whereby to continue operation of said motor for saidpredetermined period.

5. The combination according to claim 4, in which the circuit formaintaining energization of said first relay includes capacitance meansarranged to discharge to ground through the winding of said relay.

1 6. The combination according to claim 4, in which the circuit formaintaining energization of said first relay includes means foroptionally inserting additional resistance between the winding of saidrelay and ground.

7. The combination according to claim 4, including a manually operablemaster switch in the electrical circuit for energizing said first relaywinding, a glow discharge lamp, an electric circuit connecting said lampbetween said relay'winding and ground potential to energize said lampupon closure of said master switch, a momentary contact pushbuttonswitch in series with said master switch and said relay winding, andelectric circuit means for shunting out said discharge lamp upon closureof said pushbutton switch.

8. In a laundry dryer including a drum mounted for rotation to tumblearticles of clothing therein, an electric heater to facilitateevaporation of moisture from said clothes, and an electric motoroperative to rotate said drum: the combination comprising a source ofelectric power, a first relay having a winding responsive to apredetermined threshold value of electrical energy to operate saidrelay, means for temporarily energizing said relay to operate the same,switching means effective upon operation of said relay to energize saidmotor and said heater, a second relay having a winding, switching meanseffective upon operation of said first relay to energize the winding ofsaid second relay to operate the same, switching means on said secondrelay to provide a parallel energizing circuit for said electric motor,other switching means on said second relay to prepare a circuit formaintaining energization of said first relay, said last-named circuitincluding spaced electrodes within said drum in the patch of articles ofclothing being tumbled therein, said electrodes constituting a break insaid circuit adapted to be bridged by said articles, wherein theelectrical re sistance of said circuit is relatively low when thearticles are damp and relatively high when the articles are dry, thewinding of said first relay being in series with said energy maintainingcircuit and being energized above its threshold level only while theresistance of said circuit is at the said relatively low level, saidrelay therefore restoring to effect the opening of its switching meansas said articles attain dryness; said first relay having a delayedrelease time to maintain its switch means closed for the time necessaryfor articles of clothing in flight within said drum during the tumblingoperation to contact with said electrodes.

9. The combination according to claim 8, in which said electrodescomprise conductors extendingcircumferentially about the interior ofsaid drum and means for insulating said conductors from said drum whileexposing the same to articles in the drum to be electrically bridgedthereby.

10; The combiriation according to claim 8, in which said electrodescomprise aplurality of relatively closelyspaced pairs disposed atintervals along the axial length of said drum, the exposed surface ofsaid drum between any two of said electrodes beingelectricallynon-conductive.

l1. In a laundry dryer including a drum mounted for rotation to tumbleanticles of clothing therein, an electric heater to facilitateevaporation of moisture from said clothes, and an electric motor forrotating said drum: the improvement in means for terminating theoperation of said motor and said heater according to the dryness of theclothing, comprising: i

a source of electric energy,

a first relay having a winding responsive to a predeter mined thresholdvalue of electri cal energy to activate the same,

a first electric circuit, including a first manually oper able switch, adischarge lamp, and a resistor in series with said relay across saidenergy source, the re sistance of said circuit being such as to precludeoperation of said relay upon closing said switch,

a second electric circuit, including said switch, said lamp and saidresistor to effect discharge of said lamp upon closure of said switch,

a third electric circuit including said relay and a second manuallyoperable switch for shunting out said lamp while temporarily energizingsaid relay upon closure of said second switch,

an electric energy circuit including switch means actuated by said firstrelayto energize said motor and said heater upon activation of saidrelay,

a second relay,

an energy circuit including other switch means actuatcd' by said firstrelay to actuate said second relay,

an energy circuit including switch means actuated by said second relayto establish a parallel electric circuit for said motor, I

an energy circuit including further switch means actuated by said secondrelay to establish a second circuit for energizing said first relay,said second circuit including a plurality of normally open contactsadapted to be bridged by electrical conductance of the damp clothingthereacross during the tumbling thereof, whereby the maintenance of anenergized condition of said first relay is dependent upon theconductance of the damp clothing bridge and the resistance of said firstnamed electric circuit,

and means for adjusting the resistance of said first circuit to adjustthe threshold operating level of said first relay, said second relaybeing arranged to delay opening its switch completing said second motorcircuit to maintain operation of said motor for a predetermined periodfollowing deenergization of said'first relay and the opening of themotor circuit controlled thereby.

12. In a lanudry dryer including a drum mounted for rotation to tumblearticles of clothing therein, an electric heater to facilitateevaporation of moisture from said clothes, and an electric motor forrotating said drum: the improvement in means for terminating theoperation of said motor and said heater according to the dryness of theclothing, comprising:

a source of electric energy,

a firstrelay having a winding responsive to a predetermined thresholdvalue of electrical energy to activate the same,

a first electric circuit, including a first switch manually operable toeither of two operating positions, a discharge lamp, and a resistor inseries with said relay across said energy source, the resistance of saidcircuit being such as to preclude operation of said relay upon closingsaid switch to either of its operating positions,

a second electric circuit, including said switch, said lamp and saidresistor to effect discharge of said lamp upon closure of said switch,

a third electric circuit including said relay and a manually operablemomentary contactswitch for shunting out said lamp while temporarilyenergizing said relay upon closure or said second switch, said thirdcircuit including means for maintaining activation of said relay for apredetermined period following the opening of said switch,

an electric energy circuit including first switch means actuated by saidfirst relay to energize said motor and said heater upon activation ofsaid relay,

a second relay,

an energy circuit including other switch means actuated by said firstrelay to actuate said second relay,

an energy circuit including switch means actuated by said second relayto establish a parallel electric circuit for said motor,

an energy circuit including switch means actuated by said second relayto establish a second circuit for energizing said first relay, saidsecond circuit including a plurality of normally open contacts adaptedto be bridged by the electrical conductance of the damp clothingthereacross during the tumbling thereof, whereby the maintenance of anenergized condition of said first relay is dependent upon the resistanceof the damp clothing bridge and the resistance of said first namedelectric circuit,

means for establishing first and second resistance values in the relayenergizing circuit established by said second relay according to theoperating position of said manually operable switch,

said second relay being arranged to delay opening its switch completingsaid second motor circuit to maintain operation of said motor for apredetermined period following deenergization of said first relay andthe opening of the motor circuit controlled thereby.

13. In a laundry dryer including a drum mounted for rotation to tumblearticles of clothing therein, an electric heater to facilitateevaporation of moisture from said clothes, and an electric motor forrotating said drum: the improvement in means for terminating theoperation of said motor and said heater according to the dryness of theclothing, comprising:

a source of electric energy,

a first relay having a winding responsive to a predetermined thresholdvalue of electrical energy to activate the same,

a first electric circuit, including a first manually oper- 12 ableswitch, a discharge lamp, and a resistor in series with said relayacross said energy source, the resistance of said circuit being such asto preclude operation of said relay upon closing said switch,

a second electric circuit, including said switch, said switch, said lampand said resistor to effect discharge of said lamp upon closure of saidswitch,

a third electric circuit including said relay and a momentary contactswitch for shunting out said lamp while temporarily energizing saidrelay upon closure ofsaid switch, said third circuit includingaresistorcapacitor combination for maintaining said first relayactivated for an interval following the opening of said momentarycontact switch,

an electric energy circuit including first switch means actuated by saidfirst relay to energize said motor and said heater upon activation ofsaid relay,

a second relay,

anenergy circuit including other switch means actuated by said firstrelay to actuate said second relay,

an energy circuit including switch means actuated by said second relayto establish a parallel electric circuit for said motor,

an energy circuit including switch means actuated by said second relayto establish a second circuit for energizing said first relay, saidsecond circuit including a plurality of normally open contacts adaptedto be bridged by the electrical conductance of the damp clothingthereacross during the tumbling thereof, whereby the maintenance of anenergized condition of said first relay is dependent upon theconductance of the damp clothing bridge,

means for introducing a fixed additional resistance into said secondcircuit to adjust the threshold operating level or said first rela saidsecond relay being arranged to delay opening its switch completing saidsecond motor circuit to maintain operation of said motor for apredetermined period following deenergization of said first relay andthe opening of the motor circuit controlled thereby.

Retierencesv Cited in the file of this patent UNITED STATES PATENTS2,045,381 Elberty June 23, 1936 2,736,970 Engel Mar. 6, 1956 2,743,532Steward May 1, 1956 2,796,679 Dunkelman June 25, 1957 2,825,146Kostelich Mar. 4, 1958 2,863,224 Zehrbach Dec. 9, 1958 2,878,579 FuchsMar. 24, 1959

1. IN A LAUNDRY DRYER INCLUDING A DRUM MOUNTED FOR ROTATION TO TUMBLEARTICLES OF CLOTHING THEREIN, AN ELECTRIC HEATER TO FACILITATEEVAPORATION OF MOISTURE FROM SAID CLOTHES AND AN ELECTRIC MOTOROPERATIVE TO ROTATE SAID DRUM; THE COMBINATION COMPRISING A SOURCE OFELECTRIC POWER, A FIRST RELAY HAVING A WINDING RESPONSIVE TO APREDETERMINED VALUE OF ELECTRICAL ENERGY TO OPERATE SAID RELAY, ELECTRICCIRCUIT MEANS FOR FIRST TEMPORARILY ENEGIZING SAID RELAY TO OPERATE THESAME, SWITCHING MEANS EFFECTIVE UPON OPERATION OF SAID RELAY TO ENERGIZESAID MOTOR AND SAID HEATER, A SECOND RELAY HAVING A WINDING, SWITCHINGMEANS EFFECTIVE UPON OPERATION OF SAID FIRST RELAY TO ENERGIZE THEWINDING OF SAID SECOND RELAY TO OPERATE THE SAME SWITCHING MEANSOPERATED BY SAID SECOND RELAY TO PROVIDE A PARALLEL ENERGIZING CIRCUITFOR SAID ELECTRIC MOTOR, OTHER SWITCHING MEANS OPERATED BY SAID SECONDRELAY TO PREPARE A CIRCUIT FOR MAINTAINING ENERGIZATION OF SAID FIRSTRELAY, MEANS IN SAID LAST NAMED CIRCUIT RESPONSIVE TO CONTACT BY DUMPCLOTHES WITHIN SAID DRUM FOR COMPLETING SAID CIRCUIT AT AN ENERGY LEVELMAINTAINING OPERATION OF SAID FIRST RELAY AND RESPONSIVE TO A LESS DAMPCONDITION OF SAID CLOTHES TO REDUCE SAID ENERGY LEVEL BELOW THEOPERATIONAL THRESHOLD OF SAID FIRST RELAY TO THEREBY EFFECT THE OPENINGOF THE SWITCHING MEANS ASSOCIATED THEREWITH; EACH OF SAID RELAYS BEINGOF THE SLOWTO-RELEASE TYPE, WITH THE SECOND RELAY DELAYING ITS RELEASEFOR A PREDETERMINED PERIOD AFTER THE RELEASE OF THE FIRST, WHEREBY TOCONTINUE OPERATION OF SAID MOTOR FOR SAID PREDETERMINED PERIOD.